Whenever you build a balcony, a porch, a gallery, or a terrace always make
it at least six feet deep. If possible, recess at least a part of it into
the building so that it is not cantilevered out and separated from the
building by a simple line, and enclose it partially.

This instruction is preceded by a couple of hundred words of justification,
including:

Balconies and porches which are less than six feet deep are hardly ever used.

There are 253 of these patterns. They’re practical, concrete advice. They’re
generic, but they’re not abstract.

The GOF patterns are very different in character. They manage to pull off the
trick of being both very abstract and very low level. As a result, the book has
had relatively little practical impact on day-to-day software engineering,
despite its high profile.

In hindsight then, the GOF book didn’t really work. But while its low level and
abstract patterns are not useful to most of us (because they’re low level and
abstract!), they great things for language designers to bear in mind.